Invocation is a Quranic term, in all of whose usages, there is a common implied meaning. However, in most of them, there is one meaning supplemented. Some scholars have mentioned subdivisions for invocation that include even “meditation”.Invocation of God is the union with the one God and appears in a variety of manifestations. The absoluteness of “Remember me” in the Koran covers all ways of man’s remembering God. In this regard, the paper presents the interpretations of Shi`a infallible leaders and the opinions of great exegetes such as Shaykh Tusi, Tabari, Zamakhshari, Meibudi, Fakhr ar-Razi, Abulfutūh ar-Razi, Allamah Tabataba`i, and Suyuti. Moreover, the highest degree of invocation is the oblivion of the real self, the accomplishment of which is in the union with God. Invocations of man’s tongue, soul, self, mind, nature, heart, etc, are fully dealt with in this paper.